The disposal of energetic materials, such as solid rocket propellants, explosives, and pyrotechnic materials (collectively referred to hereinafter as PEP materials) has been accomplished in the past by a number of different devices and procedures. For purposes of the present invention, the words "disposal" shall include the notions implied by recovery, reprocessing, size reduction and removal of PEP materials. Such materials have presented challenging disposal problems due to the diversity of their compositions, their sizes, and the sometimes intricate variations in their operational configurations. Typically, PEP materials have included a number of propellants of different compositions such as ammonium perchlorate (plus additives), single-based propellant (nitrocellulose), double-based propellant (nitrocellulose and nitroglycerin), and triple-based propellant (nitrocellulose, nitroglycerin, and nitroguanidine). PEP materials also include explosives such as the so-called plastic bonded explosives (PBX) and pyrotechnics such as white phosphorous (WP). In addition, PEP materials used as propellants for rockets, missiles, and projectiles can range from a few inches in diameter and a few pounds in weight for tactical rockets, up to ten (10) feet in diameter and several hundred thousand pounds in weight for large strategic rocket boosters. Despite such variations, however, the disposal of all PEP materials must be done safely and with consideration for such environmental factors as waste minimization, protection of surface and groundwater, and control of air contamination. As a practical matter, the disposal should be done efficiently.
Conventional ways for disposing of such inventory include open field burning and detonation. The advantage of open field burning or detonation is that the desired result can be achieved quickly using presently available technology with a minimum cost. The environmental consequences of open field burning, however, while they may be tolerable in light of other constraints, may be undesirable and even unacceptable. This may be especially so when a substantial number or amount of inventory must be destroyed.
Another conventional method for the disposal of PEP materials is the so-called high pressure water washout method which is used to remove such materials from metal casings. Unfortunately, the aqueous output stream resulting from such washout methods complicates subsequent incineration. In addition, it can contaminate the PEP materials and it can also lead to environmental contamination problems if the aqueous output stream is not properly recovered.
Another conventional method for disposing of munitions is sawing or shearing rocket motors into smaller size chunks for incineration in a rotary kiln. Unfortunately, the frictional heating which is caused by sawing or shearing is a major concern. To help alleviate this problem, frequent liquid injections are required. Such injections, however, create an aqueous stream of contaminated waste materials which must also be properly discarded. Further, such a technique has not been proven safe for all PEP materials. While to date some development work has been done to shave PEP material from the inside of a large solid rocket motor with an apple-parer type device, the risk of ignition due to frictional heating continues to be a major drawback of this process.
The present invention thus recognizes the need for removing solid material while minimizing aqueous wastes which may be hazardous and costly for disposal. In addition, the present invention recognizes that when removing solid PEP or energetic materials, sensitivity of such materials should be reduced during removal and disposal to enhance safety.
Accordingly, it is an object of the present invention to provide a method and apparatus for cryogenic removal of solid material which minimizes the amount of hazardous waste material generated. In addition, it is yet another object of the present invention to provide a method and apparatus for removing and disposing of solid PEP and energetic material in a safe and efficacious manner, with a reduced sensitivity of the PEP material to ignition during removal. It is yet another object of the present invention to provide a method and apparatus for the disposal of energetic materials which allows the removed material to be easily transported for subsequent storage or incineration. Yet another object of the present invention is to provide a method and apparatus for cryogenic removal of solid materials which is cost-effective and easy to use.